1. Field of the Invention
The present invention relates to rotary piston engines, and more particularly to cooling systems for rotary piston engines. More specifically, the present invention pertains to cooling systems for rotary piston engines wherein cooling liquid pumps are provided to force cooling liquid through cooling liquid jackets formed in the rotary piston engines.
2. Description of the Prior Art
In Japanese utility model application No. 48-56369 filed on May 14, 1973 and published for public inspection on Jan. 17, 1975 under the disclosure No. 50-4105, there is disclosed an example of the cooling system for a rotary piston. In the structure disclosed by this Japanese utility model, a cooling liquid pump is provided on the upper portion of one of the side housings so that the cooling liquid is drawn from the radiator and forced to flow through the cooling liquid jackets in the engine.
It should however be noted that in the structure of this utility model, since the cooling liquid pump is located at the upper portion of the engine, there is a possibility that air will be drawn into the pump when the level of the cooling liquid is decreased. This trend is particularly significant in a car of recent design having a lower front profile which causes a decrease in the heightwise dimension of the front engine compartment. In this type of car, an inclined radiator arrangement is usually adopted for accommodating the radiator to the front engine compartment of decreased height, so that the cooling liquid pump is very often located above the level of the radiator and there is a high possibility that air will be drawn into the pump in a case where the pump is located at an upper portion of the engine.
If air is drawn into the cooling liquid pump, there will be a decrease in the cooling effect of the cooling liquid. Further, in a case where the level of the cooling liquid is decreased in the pump, the pump impeller will be exposed in the air space so that the pump efficiency will significantly be decreased. It should further be noted that in a structure where the pump is mounted directly on the engine casing, there will be a danger of pump overheating if the level of the cooling liquid is decreased in the pump. Thus, it is undoubtedly preferable to locate the cooling liquid pump at a lower portion of the engine. However, it is very difficult to find a proper location for the pump.
In an engine having a cover plate provided outside one of the side housings for mounting engine accessories such as a lubricant oil pump and an ignition distributor, the cooling liquid pump may be mounted on this cover plate and it may be possible to locate the cooling liquid pump at a lower portion if the pump is mounted on an outer side face of the cover plate. However, this arrangement is disadvantageous in that the overall length of the engine is undesirably increased so that inconveniencies may be encountered in arranging the engine in the engine compartment. Particularly, the problem becomes serious in a rotary piston engine having three or more rotors which has an increased axial length as compared with conventional commercial rotary piston engines.